Night vision devices are widely used in adventure, field exploration and military, etc.
In early night version devices, there is no auxiliary light source, and thermal imaging is used, by which thermal imaging images are obtained through sensing the wavelength of blackbody radiation, and converted into images visible to human eye through a display. For the devices of this period, complex cooling means are needed, the size is large, and the night vision distance is short.
With advances in light-sensitive chip and light-emitting diode (LED) illumination, night vision device using infrared LED as an auxiliary light source has been proposed, in which telescope lens is generally used, images are obtained using light-sensitive chip and displayed on a liquid crystal display (LCD), and a fixed light-output structure is generally used by the auxiliary light source. In the case that improving the image quality of the night vision device is desired, the resolution of the light-sensitive chip needs to be increased, which will lead to reduction in sensitivity and, thereby, shortening in night vision distance. In the case that zooming is used to increase the night vision distance, the auxiliary light source needs to have a corresponding illumination distance, which will lead to increase in number of the lights in order to increase illumination energy. However, when the focal length is shortened, energy waste will occur.